1. Field of the Invention
The present invention relates to an image forming apparatus, more particularly to an image forming apparatus in which same adjustment of the density of images can be carried out in two different development modes.
2. Description of the Prior Art
It is known that there are two kinds of recorded images of a microfilm i.e., positive and negative images. In order to transcribe the contents of these recorded images onto record media, such as paper sheets as a positive image, two different development modes are required.
The direction of adjustment for the image density differs between the different development modes. For instance, when the adjustment of brightness for an exposure lamp (e.g., a halogen lamp which irradiates a microfilm) is to be performed by image density adjusting means, the image becomes light when the exposure lamp is brightened in one development mode while the image becomes dark when the exposure lamp is brightened in the other development mode. Accordingly, it is desired that the adjustment of image density can be performed by a common operation means in the two different modes.
Actually, however, in order to adjust the brightness of the exposure lamp, mere use of a variable resistor or potentiometer results in the necessity of moving a knob of the variable resistor in the same direction as that of brightness or darkness of the exposure lamp. As a result, the direction of the movement about the knob of the variable resistor becomes opposite to that of the image density between the positive-positive development and the negative-positive development. Consequently, erroneous copies often tend to be made. In addition, there are other disadvantages, such as that its manipulation is not good as user's determination is required for the manipulation at each time.